838 resultados para Enantioselective Michael addition


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Abstract This paper presents the outcomes from a workshop of the European Network on the Health and Environmental Impact of Nanomaterials (NanoImpactNet). During the workshop, 45 experts in the field of safety assessment of engineered nanomaterials addressed the need to systematically study sets of engineered nanomaterials with specific metrics to generate a data set which would allow the establishment of dose-response relations. The group concluded that international cooperation and worldwide standardization of terminology, reference materials and protocols are needed to make progress in establishing lists of essential metrics. High quality data necessitates the development of harmonized study approaches and adequate reporting of data. Priority metrics can only be based on well-characterized dose-response relations derived from the systematic study of the bio-kinetics and bio-interactions of nanomaterials at both organism and (sub)-cellular levels. In addition, increased effort is needed to develop and validate analytical methods to determine these metrics in a complex matrix.

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No menos útil que la escritura de la historia para conocer lo que sucedió realmente es analizar las maneras de escribir esa misma historia para saber qué motivaciones, intenciones, fi lias o fobias latieron bajo la prosa de un historiador, un arte del que ya la misma antigüedad nos brindó excelentes ejercicios, por citar dos ejemplos ilustres, como la Maledicencia de Heródoto, de Plutarco, o el Cómo se debe escribir la historia, de Luciano de Samosata. A esa labor tan interesante se dedicó, en diciembre de 2006, un coloquio en el Institut für Geschichtswissenschaft, Abteilung Alte Geschichte de la Rheinische Friedrich- Wilhelms-Universität de Bonn y con el no menos importante motivo de festejar el octogésimo aniversario de una celebridad de la historia antigua como la del profesor Gerhard Wirth.

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An enantioselective approach to (-)-isoavenaciolide was achieved starting from 1- undecyn-3-ol. The synthesis relied upon the preparation of a chiral 4-silyloxy-2-alkenylborane by hydroboration of a protected 2,3-allenol and subsequent stereoselective addition to 2- thiophenecarboxaldehyde

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Collection : French books before 1601 ; 298.2

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Starting from (S)-tryptophanol, a formal synthesis of ent-rhyncho-phylline and ent-isorhynchophylline, involving stereoselective cyclocondensation, spirocyclization, and alkylation reactions, and the final adjustment of the oxidation level at the oxindole and piperidine moieties, is reported.

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The Iowa Medicaid Enterprise (IME) is an endeavor, started in 2005, to unite State staff with “best of breed” contractors into a performance-based model for administration of the Medicaid program.

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The Iowa Medicaid Enterprise (IME) is an endeavor, started in 2005, to unite State staff with “best of breed” contractors into a performance-based model for administration of the Medicaid program.

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Standard ecological methods (pitfall traps, trunk eclectors and soil cores) were used to evaluate collembolan community responses to different flooding intensities. Three sites of a floodplain habitat near Mainz, Germany, with different flooding regimes were investigated. The structures of collembolan communities are markedly different depending on flooding intensity. Sites more affected by flooding are dominated by hygrophilic and hygrotolerant species, whereas the hardwood floodplain is dominated by mesophilic species. The survival strategies of the hygrophilic and hygrotolerant species include egg diapause and passive drifting. The physiological adaptations to hypoxic conditions of several collembolan species were analyzed using a microcalorimeter. The activities were tested under normoxic and hypoxic/anoxic conditions as well as during post-hypoxic recovery. Lactate was increased after hypoxic intervals in the species studied, suggesting that, in addition to a massive decrease in metabolic rate, a modest glycolytic activity may be involved in the tolerance to hypoxia.